/*******************************************************************************
 * Copyright (c) 2008-2012 Eric Wuillai.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Eric Wuillai - initial API and implementation
 ******************************************************************************/
package com.tlcsdm.eclipse.copyright.model;

import java.util.ArrayList;

public class StringMatcher {
  private static final char SINGLE_WILD_CARD = '\u0000';

  private int bound = 0;
  private boolean hasLeadingStar;
  private boolean hasTrailingStar;
  private final String pattern;
  private final int patternLength;
  private String segments[];

  /**
   * StringMatcher constructor takes in a String object that is a simple
   * pattern which may contain '*' for 0 and many characters and
   * '?' for exactly one character.
   *
   * Literal '*' and '?' characters must be escaped in the pattern
   * e.g., "\*" means literal "*", etc.
   *
   * Escaping any other character (including the escape character itself),
   * just results in that character in the pattern.
   * e.g., "\a" means "a" and "\\" means "\"
   *
   * If invoking the StringMatcher with string literals in Java, don't forget
   * escape characters are represented by "\\".
   *
   * @param pattern the pattern to match text against
   */
  public StringMatcher(String pattern) {
    if ( pattern == null ) {
      throw new IllegalArgumentException();
    }
    this.pattern = pattern;
    patternLength = pattern.length();
    parseWildCards();
  }

  /**
   * @param text a simple regular expression that may only contain '?'(s)
   * @param start the starting index in the text for search, inclusive
   * @param end the stopping point of search, exclusive
   * @param p a simple regular expression that may contain '?'
   * @return the starting index in the text of the pattern , or -1 if not found
   */
  private int findPosition(String text, int start, int end, String p) {
    boolean hasWildCard = p.indexOf(SINGLE_WILD_CARD) >= 0;
    int plen = p.length();
    for (int i = start, max = end - plen; i <= max; ++i) {
      if ( hasWildCard ) {
        if ( regExpRegionMatches(text, i, p, 0, plen) )
          return i;
      } else {
        if ( text.regionMatches(true, i, p, 0, plen) )
          return i;
      }
    }
    return -1;
  }

  /**
   * Given the starting (inclusive) and the ending (exclusive) positions in the
   * <code>text</code>, determine if the given substring matches with aPattern
   * @return true if the specified portion of the text matches the pattern
   * @param text a String object that contains the substring to match
   */
  public boolean match(String text) {
    if ( text == null )
      return false;
    final int end = text.length();
    final int segmentCount = segments.length;
    if ( segmentCount == 0 && (hasLeadingStar || hasTrailingStar) ) // pattern contains only '*'(s)
      return true;
    if ( end == 0 )
      return patternLength == 0;
    if ( patternLength == 0 )
      return false;
    int currentTextPosition = 0;
    if ( (end - bound) < 0 )
      return false;
    int segmentIndex = 0;
    String current = segments[segmentIndex];

    /* process first segment */
    if ( ! hasLeadingStar ) {
      int currentLength = current.length();
      if ( ! regExpRegionMatches(text, 0, current, 0, currentLength) )
        return false;
      segmentIndex++;
      currentTextPosition = currentTextPosition + currentLength;
    }
    if ( (segmentCount == 1) && (! hasLeadingStar) && (! hasTrailingStar) ) {
      // only one segment to match, no wild cards specified
      return currentTextPosition == end;
    }
    /* process middle segments */
    while (segmentIndex < segmentCount) {
      current = segments[segmentIndex];
      int currentMatch = findPosition(text, currentTextPosition, end, current);
      if ( currentMatch < 0 )
        return false;
      currentTextPosition = currentMatch + current.length();
      segmentIndex++;
    }

    /* process final segment */
    if ( ! hasTrailingStar && currentTextPosition != end ) {
      int currentLength = current.length();
      return regExpRegionMatches(text, end - currentLength, current, 0, currentLength);
    }
    return segmentIndex == segmentCount;
  }

  /**
   * Parses the pattern into segments separated by wildcard '*' characters.
   */
  private void parseWildCards() {
    if ( pattern.startsWith("*") ) //$NON-NLS-1$
      hasLeadingStar = true;
    if ( pattern.endsWith("*") ) { //$NON-NLS-1$
      /* make sure it's not an escaped wildcard */
      if ( patternLength > 1 && pattern.charAt(patternLength - 2) != '\\' ) {
        hasTrailingStar = true;
      }
    }

    ArrayList<String> temp = new ArrayList<String>();

    int pos = 0;
    StringBuffer buf = new StringBuffer();
    while (pos < patternLength) {
      char c = pattern.charAt(pos++);
      switch (c) {
        case '\\' :
          if ( pos >= patternLength ) {
            buf.append(c);
          } else {
            char next = pattern.charAt(pos++);
            /* if it's an escape sequence */
            if ( next == '*' || next == '?' || next == '\\' ) {
              buf.append(next);
            } else {
              /* not an escape sequence, just insert literally */
              buf.append(c);
              buf.append(next);
            }
          }
          break;
        case '*' :
          if ( buf.length() > 0 ) {
            /* new segment */
            temp.add(buf.toString());
            bound += buf.length();
            buf.setLength(0);
          }
          break;
        case '?' :
          /* append special character representing single match wildcard */
          buf.append(SINGLE_WILD_CARD);
          break;
        default :
          buf.append(c);
      }
    }

    /* add last buffer to segment list */
    if (buf.length() > 0) {
      temp.add(buf.toString());
      bound += buf.length();
    }
    segments = (String[]) temp.toArray(new String[temp.size()]);
  }

  /**
   * 
   * @return boolean
   * @param text a String to match
   * @param tStart the starting index of match, inclusive
   * @param p a simple regular expression that may contain '?'
   * @param pStart The start position in the pattern
   * @param plen The length of the pattern
   */
  private boolean regExpRegionMatches(String text, int tStart, String p, int pStart, int plen) {
    while (plen-- > 0) {
      char tchar = text.charAt(tStart++);
      char pchar = p.charAt(pStart++);

      // process wild cards, skipping single wild cards
      if ( pchar == SINGLE_WILD_CARD )
        continue;
      if ( pchar == tchar )
        continue;
      if ( Character.toUpperCase(tchar) == Character.toUpperCase(pchar) )
        continue;
      // comparing after converting to upper case doesn't handle all cases;
      // also compare after converting to lower case
      if ( Character.toLowerCase(tchar) == Character.toLowerCase(pchar) )
        continue;
      return false;
    }
    return true;
  }
}
